Understanding the role of nanoparticles in boiling phase transition: The effect of nanoparticle shape

Abstract

Molecular dynamics simulation (MDS) is adopted to analyze how the nanoparticles morphology affects the fluid phase transition of nanofluid. In this simulation system, the nanochannel surfaces and nanoparticles are composed of solid copper and the base fluid is argon fluid. In addition, physical quantities such as total energy, average temperature, density, gas atomic number and thermal conductivity of these atomic structures are calculated. Through the addition of nanoparticles containing circle-, cubic-, and cylinder-shaped base fluid, it is observed that the time of phase transition onset is reduced and the rate of temperature increase increases with the decrease of specific surface area of nanoparticles, and among the nanoparticles with the same specific surface area, the cube nanoparticles have the greatest effect on the time of phase transition onset with 22.2 % reduction. The number of atoms in the gas phase after 17 ns decreases when nanoparticles are added to the Ar fluid. Conversely, increasing the specific surface area of nanoparticles reduces the temperature rise rate and prolongs the time of atomic phase transition. The nanofluid thermal conductivity is increased to 18 % in comparison with the base fluid. Increasing the specific surface area of nanoparticles enhances the perturbation of the particles. Finally, the most significant increase in thermal conductivity is observed for the cubic shape nanoparticles in comparison to the different shapes of nanoparticles. The thermal conductivity of nanofluid containing spherical, cubic, and cylindrical nanoparticles increase by 5 %, 18 %, and 16 %, respectively, by comparison with the thermal conductivity of Ar fluids. The obtained results can explain more clearly how the shape and specific surface area of nanoparticles affect the boiling phase transition of nanofluids, not only Cu-Ar nanofluids, but also other types of nanofluids.